1. Field of the Invention
The present invention relates to a piston engine, and more particularly relates to a piston engine for effectively reducing vibration.
2. Description of Related Art
A conventional piston engine always makes violent vibration due to reciprocal movement of pistons. The engineer can use four or more cylinders by arranging with alternative phases to reduce the violent vibration inherently of the piston engine. However, the conventional piston engine with multiple cylinders has several defects and shortcomings such as a complicated structure, expensive and a huge volume.
In additional, a balance shaft is arranged on a conventional piston engine to solve the violent vibration problem but has a limited efficiency. Two balance shafts mounted on two symmetrical sides of a crank are always needs to effectively reduce the vibration of a conventional piston engine but increases the volume of and the cost of manufacturing the conventional piston engine and may interfere with another components of the conventional piston engine, such as a driving device, a clutch or a gearbox during operation and the cost of arranging balance shafts on a conventional piston engine is high.
Furthermore, a suspension device is arranged on a conventional piston engine to separate the piston engine from a vehicle frame and to keep the violent vibration of the cylinders from transmitting to the vehicle frame.
A conventional piston engine with a single cylinder substantially comprises a piston assembly and a crank assembly. The piston assembly has a piston, a connecting rod, a piston pin and optional multiple piston rings. The piston can be a jacket and has a closed end and an open end. The connecting rod is extended into the piston and has a proximal end and a distal end. The piston pin is transversely mounted in the proximal end of the connecting rod. The motion of the piston assembly is reciprocal and the change of speed and acceleration of the conventional piston assembly is complicated. The inertia force of the piston assembly can be represent as A(θ)=A1ω2 cos θ+A2ω2 cos 2θ+ . . . , wherein the θ is the angle of the crank, the A1 called as first inertia, and the A2 called as second inertia and so on. The value of the A1 can be represent as Mps/2, wherein Mp is piston assembly mass and s is piston stroke.
The crank assembly is attached pivotally to the piston assembly and has a body, two counterweight blocks and multiple bearings. The body of the crank assembly is mounted with the distal end of the connecting rod of the piston assembly. The counterweight blocks are mounted around the body and abut the distal end of the connecting rod. The rotating unbalance force of the crank assembly can be presented as Mrw2, wherein, M is eccentric mass, r is eccentric distance, w is rotating speed. Usually, the engineers discuss the vibration by the moment that is represent as Mr.
A ratio of the rotating unbalance force of the crank assembly over the inertia force of the piston assembly is provided to project the balance of the conventional piston engine.
Therefore, the invention provides a piston engine to mitigate or obviate the aforementioned problems.